1. Field of the Invention
The present invention relates to an exhaust gas treatment apparatus, particularly to an exhaust gas treatment apparatus in which untreated gas is prevented from being discharged when a gas adsorbing column is exchanged.
2. Description of the Background
FIG. 5 of the present specification shows a conventional exhaust gas treatment apparatus using two gas adsorbing columns, wherein the reference numerals 1 and 2 each are a gas adsorbing column with a gas adsorbent contained in its inside, 3 to 6 each are inlet pipes and outlet pipes of these gas adsorbing columns 1 and 2, 7 is an inlet pipe connecting the inlet pipes 3 and 5 of said gas adsorbing columns 1 and 2, 8 is an outlet pipe connecting the outlet pipes 4 and 5 of said gas adsorbing columns 1 and 2, 9 is a treatment gas pipe for introducing gas to be treated into the inlet pipe 7, 10 is a treated gas discharge pipe for discharging the treated gas from said outlet pipe 8, and 3a to 6a each are a shut-off valve inserted in said pipes 3 to 6.
In such a conventional exhaust gas treatment apparatus, the shut-off valves 3a and 4a are opened and the shut-off valves 5a and 5b are closed, when the gas adsorbing column 1 is used. When the adsorbing action of the gas adsorbing column 1 is finished (broken out) and an indicator (not shown) inserted in the upper part of the gas adsorbing column 1 detects untreated gas, shut-off valves 5a and 6a are opened and the shutoff valves 4a and 3a are closed to use the other gas adsorbing column 2. The gas adsorbing column 1 is exchanged for a new one while the gas adsorbing column 2 is being used.
In the conventional exhaust gas treatment apparatus described above, however, untreated gas which exists in the adsorbing column 1 and the outlet pipe 4, may be discharged (passed) to the outside by way of the discharge pipe 10, for instance when one of the gas adsorbing columns 1 is exchanged because of its break through.
Thus, a need exists for an exhaust gas treatment apparatus which prevents untreated gas from being discharged to the outside.